Hi I am trying to learn how to use oxwall ping but I can't figure out where this code gets data from:

OW.getPing().addCommand('skeleton_ping', {
            params: {},
            before: function()
            {
                this.params.counterOldValue = counterOldValue;


            },
            after: function( data )
            {
                //alert(data);
                counterOldValue = data.counterNewValue;
                $('#skeleton_ping_counter').html(data.counterNewValue);
            }
        }).start(1000); // Time interval in milliseconds

It says data is null. Anyone please.